Railway signaling



May 15, 1923. 1,455,761

- J. S. HOLLIDAY RAILWAY SIGNALING Original Filed July 12. 1916 w 75 E u -5 51-50 3 6005 0195 c -25 7% h 256' I 1 0110 9 on Coil 00 of fianslannez-F 11 Y f [I P Q qtii a F 3 IN VEN TOR:

Aw ATTORNEY.

Patented May 15, 1923.

yfnurrs STATES JOHN S. HOLLIDAY, GE NEW." YORK, II. '51, in

Original application filed. July 12, 1916, Serial To all whom it may concern:

Be it known that 1, JOHN S. HoLLInAY, a citizen of the United States, residing at New York, in the county and State of New York, have invented certain new and u eful Improvements in Railway Signaling, of which the following is a specification.

My invention relates to railway signaling, and particularly to signaling of the type comprising alternating current track circuits.

Apparatus embodying my invention is particularly well adapted for use on railways the propulsion energy for which is alternating current. When alternating current track circuits are applied to railways of this class, the frequency of the track circuit or signaling current usually differs from that of the propulsion current. One feature of my invention is the provision in combination with the other elements of the propulsion and signaling system, of frequency selecting means interposed between the track rails and the track relay for admitting signaling current to the relay but for preventing propulsion current iironi reaching the relay.

The present application is a division of my co-pending application filed July 12, 1916, Serial No. 108770, for railway signaling and frequency selective devices for use in connection therewith.

I will describe one form of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of railway and one form of signaling system embodying my invention. Fig. 2 is a vector diagram showing the voltages across the various members and the terminals of the frequency selective device shown in Fig. 1. Fig. 8 is a group of curves showing results obtained by an experimental test of the fre quency'selective device shown in Fig. 1.

Similar reference characters refer to similar parts in each of the views.

Referring first to Fig. 1, reference characters land 5 designate the tract rails of an electric railway, which rails. are divided into sections by insulated joints 9.. In the drawing I have shown only one section A-B and the beginning and the end re- SVIITCIEZ 6 SIGNAL FENNSYLVANIA.

No. 108,770. Divided and this epplicati n filed October rial No. 4.1

spectively of the two adjoining sections. or the control of traflic through section n B I provide a signal S having a semaphore arm 20, which, when in the vertical position as shown, indicates proceed, and which, when in the horizontal position, indicates stop. These positions of the signal arm are cortrolled by a relay B, through the following circuit: from a battery E, through contact 6 of relay R, wire 8, operating mechanism (not shown) of signal S to battery The signal S.

and wire therefore, indicates proceed or stop, ac-

cordn as relay ll energized or decucrlZGd Y .rlelay 1S controlled by a track c1rcu1t ior SQCLlOIl ilB, which circuit comprises the track rails l and 5 of the section, source of signaling current connected to the rails adjacent one end of section AB and a current carrying device receiving energy from the rails near the other end of section AB. its here shown, the source of signaling current for the track circuit is a transformer M, the primary of which receives signaling current from an alternator H through a transmission line N, and the secondary of which is connected to the track rails a and 5 by wires 10 and 13 respectively. The current carrying device, as here shown. is the secondary 30 of a transformer F, the primary 31 of which is connected with the track rails through wires 11 and 12, and the secondary of which delivers this current to relay R as I shall presently describe.

ranay ll is connected to the secondary or transformer F by a frequency selecting device K comprising, in this form my invention, inductances 21 and 22, a resistance and a condenser 24. lnducla cc 2i and condenser 24 are connected to the extremities a and a respectively of the secondary 30 of transformer F, while re sistance 233 and inductance 29. are connected to an inter-nudists point Z) of this secondarv. Inductance 21 and resistance 23 are joined a terminal and hidnctance 22 and (95% i are joined at terminal. f, which are hereinafter referred to the Y) terminals current-delivery te minals. connected to terminals (Z and f, so tha voltage across these terminals is the voltage applied to the relay winding.

In the following specification and claims, for want of a more suitable term I shall use the word impedance to designate the elements 21, 22, 23 and 24. It will be understood, therefore, that whenever this term appears in the present application, it shall be construed to describe a resistor, a reactor, a condenser or any combination of the three.

The signaling or track circuit current flowing in primary 31 of transformer F induces an electromotive force of signaling current frequency in secondary 30. As will appear in detail hereinafter, this electromotive force causes currents to flow through secondary 30, reactors 21 and 22, resistance 2?), and condenser 2a, which currents result in establishing a potential difference between the current delivery terminals d and It follows that this potential difference, being applied to the terminals of relay R, causes a flow of current in the winding of this relay which is thus held in the closed position so that signal S is caused to indicate proceed.

\Vhen a vehicle V accepts this signal and enters track section A-B the wheels and axles thereof form a low resistance shunt from one rail of the section to the other. 'lranstormer F, therefore, is short circuited at the track rails and receives but a negligibly small amount of signaling current, so that relay R is de-energized and causes signal S to assume the stop indication. Thus it appears that relay R is responsive to the signaling current in tl'iIIiSfOlll'lQl' F and controls the signal S to indicate proceed or stop according to the absence of vehicles in section A-B.

Propulsion current for the operation of the cars or trains along the railway is furnished by an alternator G, one terminal of which is connected to a trolley wire or third rail L, and the other terminal of which is grounded to the track rails. This propulsion current flows from one terminal. of the generator through wire Ti, vehicle V, track rails ti. and 5 in parallel to the other terminal of the generator G. In flowing through the vehicle the current drives the propulsion motors which I have not shown on the drawing. As noted hereinbefore the track rails are divided into sections by insulated joints 2. To pass the propulsion current around these joints, without interfering with the track circuits hereinbefore described, I provide impedance bonds for the joints, each bond comprising iron core impedance coils 3 and 3 connected between the track rails. one on each side of the joints. The middle points of these coils are connected together by a conductor 3 At each bond the propulsion current enters both ends of the coil sin'mltaneously from both track rails and flows to the middle point of the coil in opposite directions. From there it flows through conductor 3 to the middle point of coil 3. Here the current divides, one half flowing through one part of coil 3 to the track rail l of the next section, and the other flowing through the other part of coil 3 in the opposite direction to the track rail 5 of that section. The propulsion current, therefore, traverses the two halves of each of the coils 3 and 3 in opposite directions so that the resultant magnetic flux in the cores of these coils is practically zero. Consequently, the impedance of these coils to the propulsion current is reduced practically to the ohmic resistance of the coil windings, which can be made very low. These impedance bonds, however, aln'iost entirely prevent the flow of signaling current from one rail to the other of a section, because this current magetizes the cores of the coils and is therefore met by a high impedance which reduces the flow of the signaling current to a small amount. Thus it is apparent that the impedance bonds offer but a small resistance to the proper flow of the propulsion current, while at the same time they prevent an improper tlow of the signaling current from section to section.

For a variety of causes, such for example as unequal bonding of the track rails, it may happen that for the propulsion current the potential of one track rail in section AB is higher than the tential of the other rail, so that a part 0 the propulsion current flows from one track rail to the other, through transformer F, and therefore, also through the impedances of the frequency selecting device K. It should here be noted that the propulsion current differs in frequency from the signaling current which normally energizes transformer F. For purposes of illustration, and to correspond with present day commercial prac tice, I shall assume herein that the frequency of the propulsion current is 25 cycles, whereas the frequency of the signaling current is (30 cycles, but it is understood that I do not wish to be limited to these values, my invention being applicable to currents of any desired frequencies.

Referring now to the vector diagram, Fig. 2, the vectors a" 7) and b 0 represent respectively the voltages in the sections a b and 7) 0 of the secondary 30 of transformer F. The point 7) is so located and the values if impedances 2i. 22, 23 and 24; are so chosen.

that it the alternating voltage across a c of the secondary 30 is of propulsion current frequency. vectors a d" and b (1" represent respectively the voltages across inipedances 21 and 23 and the voltages across impedanccs 22 and 24- are indicated respectively by vectors 7) f and c It Will be seen that the point I) and the elements 21, 22, 23

are

and 24 have been so chosen that point 7 coincides with point (2, that is, the points (Z and f have zero potential and zero phase difference between them for propulsion current frequency. It follows, therefore, that the propulsion current, even when it reaches transformer F cannot afi'ect relay R- in its control of signal S. The correct proportioning of the impedances 21, 22, 23 and 24 and the proper location of point 6 on the secondary of transformer F may be determined either by trial or by theoretical calculation,

As is well known, the reactance of a reactor or a condenser to an alternating current depends upon the frequency of that current. If, therefore, the voltage across the terminals of the secondary 30 of transformer F due to the presence of signaling current in the primary 31 is represented by vector a c, the vectors representing the signaling current voltage across the various impedances will not be the same as before. Under these conditions the signaling current voltage across a d and Z) (Z are represented by vectors a (Z and b (5 and the signaling current voltages across impedances and 24 are indicated by vectors 6 f and c f respec tively. The two points at and f on the vector diagram do not now coincide, but are removed at a distance d The length, of this vector (l f may therefore be taken as a measure of the potential difference be tween the terminals (Z and f for signaling current. which potential difference is available to cause current to pass through relay R which is thereupon energized as explained hereinbefore.

The curves in Fig. 3 (obtained by experiment) show the voltage across the currentdelivery terminals (Z and f for various 60 and 25 cycle voltages on the terminals a and c of transformer F. It is evident that the 60 cycle voltage supplied to the relay is comparatively high and approximately proportional to the 60 cycle voltage supplied to the transformer F, whereas the 25 cycle voltage at the relay remains practically zero for all values of 25 cycle voltage supplied to the transformer.

My invention is not restricted to the specific form of frequency selecting device K shown in Fig. 1. This device may be re placed by any one of a number of similar devices, some of which are illustrated and described in. my copending application referred to above and of which the present application is a division.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times, a current-carrying device receiving energy from said rails, two impedances joined in series and connected from an outside point on said device to an intermediate point thereon, two other impedances joined in series and connected from another outside point on said device to an intermediate point thereon, said impedances being so proportioned and said points being so chosen that for the propulsion current the junction points of the impedances are always at substantially equal potential, a relay connected to said junction points so that said relay is energized only by the signaling current, and a signal controlled by the relay.

2. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times, a current-carrying device receiving energy from said rails, an inductance and a resistance joined in series and connected from an outside point on said device to an intermediate point thereon, an inductance and a condenser joined in series and connected from an intermediate point on said device to another outside point thereon. said inductances, resistance and condenser being relatively so proportioned and the points at which they are connected to said current-carrying device being so chosen that for the propulsion current the junction point of the inductance and resistance is always at substantially the same potential as the junction point of the inductance and the condenser, a relay connected to said junction points so that said relay is energized only by the signaling current, and a signal con trolled by the relay.

3. In combination, the track rails of a railway, in which signaling current and propulsion current differing in frequency may flow at times, a current-carrying device receiving energy from said rails, shunts comprising series-connected iinpedances connected to points on said current-carrying device differing in potential, said shunts reacting differently to said signaling current and said propulsion current so that for the propulsion current a point on one shunt is always at substantially the same potential as a. point On the other shunt, a relay connected between said points on said shunts, and a signal controlled by said relay.

at. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times. a current carrying device receiving energy from said rails, two current delivery terminals, means interposed between said device and said terminals for causing both terminals to be at substantially the same potential for the propulsion cur rent but not for the signaling current, a relay connected with said terminals, and a signal controlled by said relay.

In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times, a current carrying device receiving energy from said rails two current delivery terminals, a combination of impedances connected between said device and said terminals and arranged to react differently to currents of said frequencies so that both terminals are at substantially the same potential for propulsion current but not for signaling current, a relay connected with said terminals, and a signal controlled by said relay.

6. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times, a current carrying device receiving energy from said rails, two current delivery terminals, impedances connected from a plurality of points different in potential on said device to said terminals and arranged so that both terminals are at substantially the same potential for propulsion but not for signaling current, a relay connected with said terminals, and a signal controlled by said relay.

7. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flow at times, a current carrying device receiving energy from said rails, two current delivery terminals, a shunt comprising se ries-connected impedances connected across one portion of said device. a second shunt comprising series-connected impedances connected across another portion of said device, said shunts reacting differently to currents of different frequencies so that for propulsion current a oint on one shunt is always at substantial y the same potential as a point on the other shunt, a relay connected with said points, and a signal controlled by said relay.

8. In combination, the track rails of a railway in which signaling current and propulsion current differing in frequency may flowat times, a current carrying device receiving energy from said rails, two current delivery terminals, a pair of impedances connected from said device to each of said terminals, said pairs of impedances being arranged to react differently to currents of different frequencies and in such manner that said terminals are always at substantially the same potential for propulsion current but not for signaling current, a relay connected with said terminals, and a signal controlled by said relay.

9. In combination. the track rails ,of a railway in which signaling current and propulsion current differing in frequency may flow at times. a current carrying device receiving energy from said rails, two impedances joined in series and connected across one portion of said device, two other impedances joined in series and connected across another portion of said device, said impedances being so proportioned and the points at which they are connected to the current carrying device being so chosen that the two junction points of the impedances are at substantially equal potential for current of propulsion frequency but not for current of signaling frequency, a relay connected with said junction points, and a signal controlled by said relay.

In testimony whereof, I affix my signature in presence of two witnesses.

JOHN S. HOLLIDAY.

\Vitnesses M. S. KIRKLAND, J. R. GILLoN. 

